Lawn mowers are in common use for cutting grass and other vegetation to a desired height. Lawn trimmers and edgers are also used to cut grass, weeds and the like along the borders of lawns, particularly where the lawn abuts an obstruction, such as a fence or a wall. Vacuum cleaners may be used in connection with lawn care for picking up clippings, but are more commonly used in household or commercial settings to suction dirt and debris from floors and carpets.
Lawn mowers or vacuum cleaners typically include a predetermined number of wheels to support the apparatus a predetermined distance above the ground, floor or other support surface. The mower housing of the device is typically adjustable to select the desired height of the cutting blade to effect the desired cut. The vacuum housing is typically adjustable to select the desired height of brushes or suction orifices to compensate for the type of flooring or the thickness or nap of the carpet. The wheels make it difficult to maneuver the apparatus around obstacles and to otherwise turn it. Self-propelled mowers or vacuum cleaners remove some of the labor involved, but considerable effort is still required to push and pull and guide the mower or the vacuum cleaner in and around radius turns and the like.
It is known in the art to provide wheel-less grass cutting apparatus, which have a power operated rotary cutter and commonly driven air impelling means for causing air to be introduced into the mower housing and directed downward toward the ground to produce a reaction force with the ground (the so-called "ground effect"), thereby supporting the mower a small distance above the ground on a cushion of air. Air floated vacuum cleaners have not previously been known.
Prior art "air-cushioned" lawn mowers typically have a relatively narrow bottom surface or border in facing relationship with the ground, during operation, air pressure blown toward the ground by the air impelling means tends to escape from the housing between the ground and bottom surface, which substantially reduces the lifting force on the housing. The rapid escape of air along the periphery of the mower housing also stirs up debris and dust when mowing around shrubbery and the like, which makes mowing difficult and hazardous. This effect is completely contrary to the desired effect for vacuum cleaning such that it has not previously been seriously attempted. Also, because the air is blown downward to keep the housing afloat, the air pressure depresses the materials on the support surface below such as the grass, causing the cutting blade to leave an uneven cut. Other problems associated with prior art air-cushioned lawn mowers include the problem of keeping the mower on a straight cutting path and the mower housing level. Any tilting action on the housing results in an uneven cut.
The relatively narrow bottom surface of the housing also causes the mower to sink relatively deep into the grass when the mower is not in operation. As a result, upon start-up, the cutting blade will tend to "scalp" a section of the grass until it rises up to the desired cutting height by air pressure within the housing. Whether the mower is wheeled or air floated only a relatively narrow bottom surface of the housing acts to shield the internal rotating parts such as the cutting blade from the surrounding area which may be accessible to the operator. An object, such as a user's foot, might through carelessness extend past the narrow bottom surface of the housing, thereby potentially resulting in an accidental injury to the user by contact with the internal rotating mechanism especially in the case of a cutting blade.
Another disadvantage of prior art air pressure operated apparatus such as air-cushioned mowers is their inability to discharge materials such as grass cuttings through an appropriate port, or into a receptacle which leaves a windrow of grass cuttings. Conventional lawn mowers tend to vacuum up grass by the rotary action of the cutting blade, whereas in prior art air-cushioned mowers, the downwardly blown air which creates the lifting force by ground effect is not sufficient to effectively discharge grass cuttings primarily because of the escape of air from the housing. Also, the downwardly blown air tends to blow large pieces or clippings of cut, uncut, or partially cut grass downward toward the ground, which further detracts from the grass catching capability of prior art air-cushioned mowers.
Another disadvantage of prior art is that vacuum cleaner flotation was not adequately obtainable. Flotation of a vacuum cleaner has now been found to require two opposing forces, air pressure or lift or flotation simultaneously in combination with suction or vacuum means. Prior devices were not capable of adequately and simply creating and maintaining both pressure and suction simultaneously.